Glycopeptide antibiotics, which have a complex polycyclic peptide structure, are produced in various microorganism and effective to most gram-positive bacteria as an antimicrobial. In recent years, there are emergences of drug-resistant strains such as penicillin-resistant, cephalosporin-resistant, and serious problems of infections with multidrug resistant and methicillin-resistant Staphylococcus aureus (MRSA) has been raised in clinical practice. Glycopeptide antibiotics, such as vancomycin, are effective typically to these resistant strains, and vancomycin has been a drug as an ultimate tool for infections with MRSA and other resistant strains.
In certain strains, however, there is growing concern of emergence of resistance to vancomycin, such as vancomycin-resistant enterococci (VRE). VRE has a different mechanism and degree of resistance, depending on the gene type of a resistance-related gene such as Van A, B, C, D, E, G. For example, teicoplanin, which is a glycopeptide antibiotic as with vancomycin, is effective to Van B type VRE. On the other hand, effective glycopeptide antibiotic has not been released for Van A type VRE, while clinical measures to fight such resistant strain is especially needed. Furthermore, Staphylococcus aureus that has acquired the resistance of VRE (VRSA) has been discovered recently. Therefore, need for development of glycopeptide derivative having improved activity and/or selectivity exists. Many vancomycins and other glycopeptide derivatives have been known in the art. See, e.g., references as follows.    (1) Japanese Patent Publication 61-251699    (2) Japanese Patent Publication 7-258289    (3) WO96/30401    (4) WO00/39156    (5) Japanese Patent Publication 2000-302687    (6) WO2004/44222    (7) WO2001/81372    (8) WO2006/057303